In the aerosol container industry fluorocarbons or hydrocarbons are typically utilized as the propellant in a pressurized aerosol container because these compounds are generally soluble with the product to be dispensed. These compounds remain in such a soluble state whatever amount of the product is expelled from the can thereby maintaining essentially a constant pressure within the container. In this way a constant pressure is generally available to dispense the product when the valve is actuated by a user, no matter how depleted the product in the container has become. However, due to the potential environmental harm which can be caused by the fluorocarbons and hydrocarbons to the environment, there has been increasing pressure in the market to replace the fluorocarbons and hydrocarbons with more benign propellants.
Various attempts have been made to utilize compressed gases as the propellant for dispensing the product contents of a pressurized container instead of fluorocarbons, compressed air, CO2 or N2 for example. However, one major drawback associated with utilizing a compressed gas is that these gases are generally not soluble in the product. Thus, as the product contents are gradually dispensed from the pressurized container over time, the internal pressure within the pressurized container also gradually decreases. The reduction in the internal pressure of the pressurized container significantly reduces the flow rate of the remaining product contents from the pressurized container. The pressure may even drop so low as to not be able to expel any further product from the container.
For example, with such compressed gases where a container is pressurized with an initial pressure of 100 psi of pressurized gas, such as air, the product will dispense initially at the intended flow rate from the pressurized container. However, as the product contents are gradually dispensed over time, the volume in the container for the compressed gas expands and the internal pressure of the container for forcing out the product gradually decreases to, for example, only 20 psi. As a result of this reduction in dispensing pressure, the flow rate of the remaining product also decreases and the product then has a tendency to trickle out of the valve as such product is dispensed. The significant pressure drop and decrease in product flow rate is generally unacceptable and has hindered the use of compressed gases in conventional valves and pressurized containers.